/*
 * FreeModbus Libary: A portable Modbus implementation for Modbus ASCII/RTU.
 * Copyright (c) 2006 Christian Walter <wolti@sil.at>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * File: $Id: mbtcp.c,v 1.3 2006/12/07 22:10:34 wolti Exp $
 */

/* ----------------------- System includes ----------------------------------*/
#include "stdlib.h"
#include "string.h"

/* ----------------------- Platform includes --------------------------------*/
#include "port.h"

/* ----------------------- Modbus includes ----------------------------------*/
#include "mb.h"
#include "mbconfig.h"
#include "mbtcp.h"
#include "mbframe.h"
#include "mbport.h"

#if MB_SLAVE_TCP_ENABLED > 0

/* ----------------------- Defines ------------------------------------------*/

/* ----------------------- MBAP Header --------------------------------------*/
/*
 *
 * <------------------------ MODBUS TCP/IP ADU(1) ------------------------->
 *              <----------- MODBUS PDU (1') ---------------->
 *  +-----------+---------------+------------------------------------------+
 *  | TID | PID | Length | UID  |Code | Data                               |
 *  +-----------+---------------+------------------------------------------+
 *  |     |     |        |      |
 * (2)   (3)   (4)      (5)    (6)
 *
 * (2)  ... MB_TCP_TID          = 0 (Transaction Identifier - 2 Byte)
 * (3)  ... MB_TCP_PID          = 2 (Protocol Identifier - 2 Byte)
 * (4)  ... MB_TCP_LEN          = 4 (Number of bytes - 2 Byte)
 * (5)  ... MB_TCP_UID          = 6 (Unit Identifier - 1 Byte)
 * (6)  ... MB_TCP_FUNC         = 7 (Modbus Function Code)
 *
 * (1)  ... Modbus TCP/IP Application Data Unit
 * (1') ... Modbus Protocol Data Unit
 */

#define MB_TCP_TID          0
#define MB_TCP_PID          2
#define MB_TCP_LEN          4
#define MB_TCP_UID          6
#define MB_TCP_FUNC         7

#define MB_TCP_PROTOCOL_ID  0   /* 0 = Modbus Protocol */


/* ----------------------- Start implementation -----------------------------*/
eMBErrorCode
eMBTCPDoInit(USHORT ucTCPPort)
{
	eMBErrorCode    eStatus = MB_ENOERR;

	if(xMBTCPPortInit(ucTCPPort) == FALSE) {
		eStatus = MB_EPORTERR;
	}

	return eStatus;
}

void
eMBTCPStart(void)
{
}

void
eMBTCPStop(void)
{
	/* Make sure that no more clients are connected. */
	vMBTCPPortDisable();
}

eMBErrorCode
eMBTCPReceive(UCHAR* pucRcvAddress, UCHAR** ppucFrame, USHORT* pusLength)
{
	eMBErrorCode    eStatus = MB_EIO;
	UCHAR*          pucMBTCPFrame;
	USHORT          usLength;
	USHORT          usPID;

	if(xMBTCPPortGetRequest(&pucMBTCPFrame, &usLength) != FALSE) {
		usPID = pucMBTCPFrame[MB_TCP_PID] << 8U;
		usPID |= pucMBTCPFrame[MB_TCP_PID + 1];

		if(usPID == MB_TCP_PROTOCOL_ID) {
			*ppucFrame = &pucMBTCPFrame[MB_TCP_FUNC];
			*pusLength = usLength - MB_TCP_FUNC;
			eStatus = MB_ENOERR;

			/* Modbus TCP does not use any addresses. Fake the source address such
			 * that the processing part deals with this frame.
			 */
			*pucRcvAddress = MB_TCP_PSEUDO_ADDRESS;
		}
	} else {
		eStatus = MB_EIO;
	}

	return eStatus;
}

eMBErrorCode
eMBTCPSend(UCHAR _unused, const UCHAR* pucFrame, USHORT usLength)
{
	eMBErrorCode    eStatus = MB_ENOERR;
	UCHAR*          pucMBTCPFrame = (UCHAR*) pucFrame - MB_TCP_FUNC;
	USHORT          usTCPLength = usLength + MB_TCP_FUNC;

	/* The MBAP header is already initialized because the caller calls this
	 * function with the buffer returned by the previous call. Therefore we
	 * only have to update the length in the header. Note that the length
	 * header includes the size of the Modbus PDU and the UID Byte. Therefore
	 * the length is usLength plus one.
	 */
	pucMBTCPFrame[MB_TCP_LEN] = (usLength + 1) >> 8U;
	pucMBTCPFrame[MB_TCP_LEN + 1] = (usLength + 1) & 0xFF;

	if(xMBTCPPortSendResponse(pucMBTCPFrame, usTCPLength) == FALSE) {
		eStatus = MB_EIO;
	}

	return eStatus;
}

#endif
